Speed controller for a motor vehicle

ABSTRACT

A cruise controller is provided, which regulates the driving speed of the vehicle not only beyond a certain minimum speed but also at speeds below a preselected critical speed down to standstill of the vehicle. Detecting the traffic situation using a distance sensor allows the vehicle to be automatically started once the driver has responded to a corresponding starting instruction. The starting instruction is effective until a preselected time limit, but, alternatively may also be repeated. However, in any traffic situation, the driver may override the cruise controller by operating the accelerator pedal or the brake pedal.

FIELD OF THE INVENTION

The present invention relates to a cruise controller having a distancesensor for controlling the speed or acceleration of a vehicle.

BACKGROUND INFORMATION

It is believed that cruise controllers, with which a desired drivingspeed is preselectable, are known, including cruise controllers thatregulate the speed as a function of a vehicle driving ahead. Forexample, German Published Patent Application No. 196 46 104 describes adevice for selecting and displaying speeds, including a first controlunit for regulating the speed and/or acceleration of a vehicle. A secondcontrol unit controls the display of the instantaneous speed and thepreselected desired speed. This cruise controller also operates as afunction of a distance regulator (ACC, adaptive cruise control) andregulates the driving speed of the vehicle in accordance with a vehicledriving ahead. This system functions satisfactorily if the driving routeis relatively free and it is possible to drive without interruption,e.g., on a rural road or a highway. However, if there are areas oftraffic congestion or if the speed drops below a preselected limit, thecruise controller shuts down, thereby forcing the driver to manuallyregulate his driving speed according to the prevailing trafficsituation. Drivers may not be able to use this cruise controller in astop-and-go operation, for example, when starting and braking in a lowspeed range.

SUMMARY OF THE INVENTION

It is believed that an exemplary cruise controller according to thepresent invention has the advantage over the related art in that it mayalso operate in stop-and-go operation, therefore eliminating the needfor starting and braking, which may annoy the driver, e.g., when drivingin a queue. For example, it is believed that this cruise controller mayadvantageously permit automatic starting of the vehicle from astandstill, for example, if the traffic situation allows, eitherautomatically or after being enabled by the driver.

The status for stop-and-go mode may be displayed. Therefore, the drivermay retain an overview over the instantaneous functionality of thecruise controller and may decide whether to intervene or whether toallow the cruise controller to respond to stationary objects, forexample.

It is believed that the instantaneous status of the cruise controller instop-and-go mode may be advantageously displayed by a simple displayelement or signal lamp. Thus, the driver need not concentrate on otherlamps, while nevertheless advantageously retaining a full overview.

Since the driver should always retain the uppermost functional powerover the performance of the vehicle in all driving situations, thecommand for automatic starting of the vehicle to the control may bedelivered by operating a stop-and-go button. The driver may thus checkagain to determine whether the current traffic situation may permitautomatic starting of the vehicle.

To prevent automatic starting of the vehicle due to accidental operationof the stop-and-go button, the readiness for automatic starting may beshut off after a preselected period of time.

The control may repeatedly deliver a new starting instruction for thedriver, so that the driver will have enough time to respond to theprevailing traffic situation.

Another signal lamp may be provided for the status of the control in theACC mode. The additional signal lamp, for example, may be equipped withthree status messages for stop-and-go operation, like the signal lamp.Therefore, the driver retains a clear arrangement of signal lamps andmay be able to familiarize himself rapidly with the operating status ofthe cruise controller without any great learning effort.

The driver should be able to cancel the instantaneous operating state ofthe cruise controller by operating the brake, so that control of thevehicle is retained.

The individual operating elements of the cruise controller are onlyactively operable if the respective signal lamp has previously been inthe intermediate status. This may make it easier to avoid mistakes inoperation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the basic design of a cruisecontroller.

FIG. 2 is a diagram showing the speed range for which a speed v2 isgreater than a speed v1.

FIG. 3 is a state diagram showing the function of a first exemplaryembodiment according to the present invention.

FIG. 4 is a state diagram showing the function of a second exemplaryembodiment according to the present invention.

DETAILED DESCRIPTION

The block diagram in FIG. 1 shows the basic design of a cruisecontroller 50. The central unit is a control 40, which is connected to adistance sensor 41. Distance sensor 41 may be, for example, a radarsensor that works with microwaves or an optical sensor that monitors thedriving range in front of the vehicle with respect to stationaryobstacles, oncoming vehicles and vehicles driving ahead, and deliversthe corresponding information to control 40. Control 40 is connected bya corresponding interface to various vehicle components, such as enginecontrol and transmission control, brakes, etc. These units are not shownin FIG. 1 for reasons of simplicity. In its individual components,control 40 may be regarded as a cruise controller like that referred toin German Published Patent Application No. 196 46 104, for example. Assuch, no further explanation is provided. Control 40 is also connectedto operating elements, such as buttons or switches. A known cruisecontroller may have, for example, an on/off button 42, one + button andone − button 43 for selecting the last speed set and a resume button 44for restoring the set driving speed. An object of an exemplaryembodiment according to the present invention is to provide anadditional button, i.e., stop-and-go button 45. The exact function ofthis button in conjunction with the other buttons is explained in detailbelow. It should be noted that suitable switches or operating elementsmay be used instead of the buttons.

For providing the driver with information, control 40 includes displayelements 46 for the ACC mode and 47 for the status in stop-and-go mode.Additional displays for the operating function of control 40 may also beadded, for example.

However, the number of display and operating elements should be kept aslow as possible to prevent a complicated learning procedure for thedriver, and the operation should be simple enough so that it does notconstitute a safety risk. Signal lamps 46 and 47 therefore alternativelydisplay three functions. In one exemplary embodiment, the three statesare signal lamp on, signal lamp off and signal lamp having a weakenedluminous power or a different color from the on state. Alternatively,three different colors, e.g., red, green and yellow or similarembodiments may also be selected.

To explain the functioning of the embodiments, the nature of theinvention should first be explained again. A known cruise controller(FGR) may be active only above a first critical speed v1. Thus, thecontroller regulates the driving speed only when it has reached criticalspeed vi (active or activatable ACC mode). Also, in city traffic, forexample, distance sensor 41 may not always know exactly which targets itmust consider, e.g., when driving in a queue and with extremely shortintervehicle distances, e.g., at streetlights and intersections.However, cruise control is much simpler on rural roads and highways,where speeds are higher but the distances and thus the vehicle densityare lower, because it is easier to anticipate the driving behavior ofthe other drivers.

However, various exemplary embodiments according to the presentinvention may also regulate the speed range in effect from a standstillto a second critical speed v2 with an additional stop-and-go device atlow speeds, such as occur in town traffic. This stop-and-go mode isbelow second critical speed v2 if the driver has not turned the systemoff, so that it automatically regulates its distance and driving speed.

For a better understanding, the essential features of the cruisecontroller are explained below.

1. In the ACC mode, i.e., in the speed range above critical speed v1,stationary targets are also detected, but the system does not respond tothese targets. In stop-and-go mode, however, in the speed range lessthan v2, the cruise controller responds to both slow and stationarytargets which are classified as relevant.

The speed range between speeds v1 and v2 may be important if v1 is lessthan v2. In this range, the driver may choose between the two activemodes mentioned above, or alternatively may leave the choice to thecruise controller. This regulation advantageously provides a fluidtransition between the two states, and the driver may determine thepoint in time for the change in state because the driver is informedregarding the prevailing status.

2. For stop-and-go mode, the following features are also provided. Afterreaching a standstill in regulated operation, automatic starting ispossible up to a certain predetermined time limit t_(limit) afterstopping. Automatic starting is then possible only after being enabledby the driver.

3. In addition, at standstill, the cruise controller gives startinginstructions when acquisition of the object data detects an end of thestandstill situation. This may be the case, for example, when thedistance from a vehicle driving ahead has increased or when a certaindifferential speed between the two vehicles has been determined. Onlythen is automatic starting possible within a certain period of timeafter being enabled by the driver.

4. In addition, in a first exemplary embodiment according to the presentinvention, if the starting instruction is disregarded, the cruisecontroller deactivates itself, and then the vehicle may be started onlyby the driver.

In a second embodiment according to the present invention, however,there is no automatic deactivation of the cruise controller. Instead,after a preselected period of time, the driver again receives startinginstructions, if allowed by traffic conditions.

5. In addition, the driver should confirm a transition from a modehaving a lower functionality, e.g., from a stop-and-go mode, forexample, to the ACC mode. Supporting instructions by the cruisecontroller may also be possible.

6. In this exemplary embodiment, the operating elements and displays arearranged clearly and their functions are readily understandable for thedriver. Therefore, the driver has a general overview of the system.

7. All the operating elements have the same functionality in each modeto simplify operation.

8. The same is also true of the display elements, which actively informthe driver regarding the prevailing operating status, e.g., stop-and-gomode, so that the driver retains an overview of which states arefeasible.

9. It may be important that any active control mode may be overridden orturned off by the driver at any time.

FIG. 2 shows a diagram for the speed range for which speed v2 is greaterthan speed v1. The arrows show the two ranges in which the ACC mode orthe stop-and-go mode is active or may be activated. Transition rangev1<v<v2 is shown with hatching.

Two embodiments of the present invention are explained in greater detailwith reference to FIGS. 3 and 4. These two embodiments are examples ofcruise controllers that essentially fulfil features 1 through 9mentioned above.

The first exemplary embodiment according to the flow chart in FIG. 3 isexplained in greater detail first. It should be noted that FIG. 3 isbased on the intensity of the driver's intervention (horizontal axis atthe upper edge of the page): “active,” “overridden,” “activatable,” “notactivatable.” Velocity “V=0,” “0<V<v1,”. “v1<V<v2” and “v2<V” areplotted on the vertical axis on the left side, from top to bottom. Inaddition, the different symbols for signal lamps 46 and 47 for thevarious ACC modes and stop-and-go modes are shown at the lower edge ofFIG. 3. In addition, operating elements 42 through 45 with theirfunctions are also shown. Likewise, the state symbols are shown.

For reasons of simplicity, all transitions from the active state to aninactive state, which may always be triggered by operation of the offbutton or the brake pedal, are also shown in FIG. 3, but are not shownin their course. Only the condition to which such an operation leads isshown for each speed level. This exemplary embodiment uses operating anddisplay elements of conventional cruise controllers, so that noexcessive relearning effort is necessary for the driver.

The cruise controller has been expanded by adding signal lamps 46 and 47and stop-and-go button 45.

Signal lamp 46 for the distance regulator (ACC mode) may assume threeoperating modes:

The ACC lamp is off, i.e., the functionality of control 40 is neitheractive nor activatable here.

The ACC lamp is turned on: the system is in ACC mode, i.e., the ACCcontroller is active.

The ACC lamp is in an intermediate state (e.g., the lamp burns faintly,or in the case of a surface display element, only the border is shown oranother color change is discernible): the ACC mode is not active, but itmay be activated by the driver by operation of the ACC button.

Signal lamp 47 for stop-and-go mode has also been designed for threefunctions accordingly:

The stop-and-go lamp is off: the functionality of the stop-and-goregulator contained in control 40 is neither active nor activatable.

The stop-and-go lamp is on: the system is in stop-and-go mode, i.e., thestop-and-go regulator contained in control 40 is active.

The stop-and-go lamp is in an intermediate state (like signal lamp 46):the stop-and-go mode is not active, but it may be activated by thedriver by operation of stop-and-go button 45.

For example, an acoustic signal may be provided as the startinginstruction if the system detects a situation in which the systemfunctionality may be approached accordingly and preselected time limitt_(max) for automatic starting has not yet elapsed. This occurs when thesystem has braked to a standstill. Simultaneously, the driver isvisually instructed by signal lamp 47, with its intermediate state, thatcruise controller 50 is now activatable.

The function of the additional operating elements are explained below.ACC button 44 (known as a resume button) causes the ACC mode to beactivated when the driver operates this button if signal lamp 46 is inthe intermediate state.

The +/− buttons determine which actions will be implemented, dependingon the status of the system. If the cruise controller is active, i.e.,if one of signal lamps 46 and 47 lights up, then the set speed isincremented or decremented by a certain amount, e.g., 10 km/h. However,if the cruise controller is only activatable (signal lamp 46 and 47 isin an intermediate state), then the corresponding mode is activated. Theset speed is set at the next higher or lower mark relative to theprevailing speed. However, if both modes are activatable (both signallamps 46 and 47 are in an intermediate state), operation of the + buttoncauses the ACC mode to be activated. However, operation of the − buttoncauses the stop-and-go mode to be activated. Cruise controller 50 isdeactivated by operating on/off button 42.

Stop-and-go button 45 enables the driver to activate the stop-and-gomode if signal lamp 47 is in the intermediate state.

In another exemplary embodiment according to the present invention, thebuttons and the signal lamps are either mounted separately from oneanother or designed as modules.

With regard to the flow chart of FIG. 3, all the system states arerepresented either by rectangles or by ellipses.

Rectangles indicate that the vehicle is stationary and ellipses indicatethat the vehicle is in motion. In addition, the status of two signallamps 46, 47 are indicated. The transitions between the states arecharacterized with the respective buttons if the buttons may trigger thetransitions. The transition is triggered by operation of one of thesebuttons.

The features mentioned above may be implemented on the basis of the flowchart in FIG. 3 for the first exemplary embodiment. If the vehicle stopsbehind a stationary target object (a vehicle driving in front) in activestop-and-go mode, the control goes to position 1 in which thestop-and-go mode remains active. The vehicle driving in front (targetobject) approaches within time t_(limit). Then, automatic startingbegins, with cruise controller being active in the stop-and-go mode(position 2) and the speed being regulated. Simultaneously, signal lamp47 (position 33) lights up to display that the stop-and-go mode isactive. If the speed is increased further until V>v1, then in position3, lamp 31 also lights up (intermediate state) to signal that ACC modeis activatable. The driver may then choose to activate ACC mode(position 4) by operating button 44. Signal lamp 46 lights up and signallamp 47 goes into the intermediate state (position 34). If the speed isincreased further beyond critical speed v2, the ACC mode is active(position 5) and the system regulates the speed. Signal lamp 47 goesout.

If the driver, now in position 2, desires to influence the accelerationby depressing the accelerator pedal, then the driver is overriding thefunction of the stop-and-go mode (position 6). The speed of the vehicleis then increased beyond critical speed v1. In position 7, the driverfurther overrides the stop-and-go function, so that, with increasingspeed, by selecting button 44, the system again goes to position 8,where the ACC mode is active and stop-and-go mode is activatable. Hereagain, the speed of the vehicle may be increased by pressing button 43(position 9).

If the vehicle is stationary in position 1 for a period of time longerthan preselected period of time t_(limit), the system does not go intothe active state (position 11). If the prerequisites for safe startingare met, then in position 13 the stop-and-go mode is switched toactivatable and a starting instruction is issued. Signal lamp 47 is inthe intermediate mode. Within preselected time limit t_(max), the cruisecontroller may be activated and started by operating stop-and-go button45, so that the flow chart may be continued to position 2. If there isno confirmation of the starting instruction by pressing the stop-and-gobutton within t_(max), the system goes to the inactive state (position12), in which it is possible to start only by operating the acceleratorpedal. In any case, cruise controller 50 may be deactivated by operatingon/off button 42. Depending on the driving speed, the system then goesto an inactive position 12, 14, 15 or 16. The display elements do notshow an active state. However, activatability of the stop-and-go mode isindicated by the intermediate state of signal lamp 47 in position 14,activatability of the ACC mode is indicated by the intermediate state ofsignal lamp 46 in position 10, and activatability of both states(stop-and-go mode and ACC mode) is indicated by the intermediate stateof both signal lamps (46 and 47) in position 15. By operation of therespective operating elements, it is then possible to switch back to anactive state. Likewise, cruise controller 50 may be deactivated byoperating the brake pedal at any time.

Depending on the driving speed, this leads to an inactive position 10,17, 18 or 19. Both display elements 46, 47 indicate an inactive stateand no activatability. Only after releasing the brake does the systemreturn to position 14, 15 or 16, which indicate activatability and thusallow activation.

A second exemplary embodiment according to the present invention isdescribed below with reference to FIG. 4. The second exemplaryembodiment operates similarly to the exemplary embodiment describedabove, except that this embodiment differs only in that position 11 isnot provided.

The other positions are identical. Thus, in the active standing mode, anew starting instruction is delivered (position 13) when preselectedtime t_(max) has been exceeded. The driver may then decide whether toswitch to active stop-and-go mode by operating stop-and-go button 45, toleave the system inactive or to drive forward by depressing theaccelerator himself (position 14).

In summary, the essential features of these two embodiments areexplained again below, based on features 1 through 9 described above.

1. The active ACC mode includes the states “ACC active, systemregulating” (positions 4 and 5) and “ACC active, driver overriding”(positions 8 and 9) and it may be activated only above speed vl. Activestop-and-go mode includes the states “stop-and-go active, systemregulating” (positions 2 and 3), “stop-and-go active, driver overriding”(positions 6 and 7) and “stop-and-go active, target object, v=0,t≦t_(limit)” (position 1). Stop-and-go mode may be used in the speedrange below v2. These two embodiments differ in that, in the secondembodiment, activation at a standstill is also possible if the driverhas braked to a standstill. In contrast, activatability is possible at astandstill in the first embodiment only if the system was active whenstopping the vehicle. FIGS. 3 and 4 indicate that a transition to theother mode may be initiated by the driver in the speed range between v1and v2 by operating the ACC or stop-and-go buttons. Signal lamps 46, 47indicate the possibilities of a transition.

2. The mechanism described here includes the states “stop-and-go, systemregulating” (position 2), “stop-and-go active, target object, V=0,T≦T_(limit)” (position 1), “active standing” (position 11, 12) and“stop-and-go activatable, V=0, starting instruction” (position 13).

3. The mechanism described occurs in the state “stop-and-go active, V=0,starting instruction” (position 13).

4. In the first embodiment, with a given starting instruction and aftera preselected time limit t_(max) has elapsed, the system is deactivatedif it has not yet been activated by the driver, and the system may beswitched back on again by the driver only after starting. In the secondexemplary embodiment, the system remains in readiness if the startinginstruction is disregarded and preselected time limit t_(max) haselapsed, and it may optionally issue a starting instruction again andmay then change to the activatable mode.

5. A transition from stop-and-go mode to ACC mode may be accomplishedonly by explicit operation of ACC button 44.

6. The states and the respective system functionalities are notdependent upon traffic situations.

7.+8. All the operating elements and display elements have the samefunction, regardless of the prevailing state.

9. FIGS. 1 through 4 illustrate the possibilities of overriding by ahigher acceleration request on the part of the driver when the vehicleis moving or by operation of the accelerator pedal at a standstill. Whenthe vehicle is moving, operation of on/off button 42 leads to a state inwhich the system is inactive but it remains activatable at any time.

When the vehicle is stationary, on/off button 42, in the secondexemplary embodiment leads to a state in which the system is notdirectly activatable but may be activated only after a startinginstruction. For the first exemplary embodiment, operation of on/offbutton 42 when the vehicle is standing still converts it to an inactivestate in which activatability is no longer possible. On operation of thebrake by the driver, the system is transferred at any time to the statein which it is not active and is not activatable as long as the brakeremains operated.

What is claimed is:
 1. A cruise controller for a motor vehicle,comprising: a control arrangement for controlling one of a speed and anacceleration of the vehicle; a distance sensor; a display; at least oneoperating element for inputting a desired speed; and a display elementoperable to assume three different operating states for threecorresponding functions of the control arrangement in the secondoperating mode, the three operating states including: adisplay-element-off operating state, in which the second operating modeis not activatable, a display-element-on operating state, in which thesecond operating mode is active, and an intermediate state, in which thecruise controller is in an inactive state, but is activatable; whereinthe control arrangement controls the speed of the vehicle as an adaptivecruise control in a third operating mode, the third operating mode beingactive above a critical speed, and wherein, in a first operating mode,the control arrangement controls the speed of the vehicle as a cruisecontroller, and in a second operating mode, the control arrangement atleast one of: i) starts the vehicle from a standstill up to apreselected maximum speed, and ii) brakes the vehicle to a standstill.2. The cruise controller according to claim 1, wherein the speed of thevehicle is controlled in the first operating mode only above a criticalspeed.
 3. The cruise controller according to claim 2, wherein thecritical speed of the first operating mode is lower than the preselectedmaximum speed of the second operating mode.
 4. The cruise controlleraccording to claim 1, wherein a current operating mode of the controlarrangement is displayed to a driver at least one of visually andacoustically.
 5. The cruise controller according to claim 1, wherein thecontrol arrangement initiates automatic starting of the vehicle onlyafter being enabled by a driver.
 6. The cruise controller according toclaim 5, wherein a stop-and-go button is provided, and wherein automaticstarting is enabled by operating the stop-and-go button.
 7. The cruisecontroller according to claim 1, wherein the control arrangementswitches off a readiness for automatic starting of the vehicle after apreselected period of time has elapsed.
 8. The cruise controlleraccording to claim 1, wherein a starting instruction may be output for adriver.
 9. The cruise controller according to claim 1, furthercomprising a second display element operable to display a status of thecontrol arrangement in the third operating mode.
 10. The cruisecontroller according to claim 1, wherein a current operating mode iscanceled when signals are received from a brake.
 11. The cruisecontroller according to claim 1, wherein the at least one operatingelement is operable for at least one of the second and third operatingmodes only when a respective display element is in the intermediatestate.
 12. The cruise controller according to claim 1, wherein thedistance sensor includes one of a radar sensor and a light-opticalsensor.
 13. A cruise controller for a motor vehicle, comprising: acontrol arrangement for controlling one of a speed and an accelerationof the vehicle; at least one operating element for inputting a desiredspeed, wherein, in a first operating mode, the control arrangementcontrols the speed of the vehicle as a cruise controller, and in asecond operating mode, the control arrangement at least one of: i)starts the vehicle from a standstill up to a preselected maximum speed,and ii) brakes the vehicle to a standstill; and a display elementoperable to assume three different operating states for threecorresponding functions of the control arrangement in the secondoperating mode, the three operating states including: adisplay-element-off operating state, in which the second operating modeis not activatable, a display-element-on operating state, in which thesecond operating mode is active, and an intermediate state, in which thecruise controller is in an inactive state, but is activatable.
 14. Anoperating-and-display system for a cruise controller of a motor vehicle,including a control arrangement for controlling one of a speed and anacceleration of the vehicle, a distance sensor, a display, at least oneoperating element for inputting a desired speed, in which the controlarrangement controls the speed of the vehicle as a cruise controller ina first operating mode and, in a second operating mode, at least one of:i) starts the vehicle from a standstill up to a preselected maximumspeed, and ii) brakes the vehicle to a standstill in a second operatingmode, the system comprising: a display element operable to assume threedifferent operating states for three corresponding functions of thecontrol arrangement in the second operating mode, the three operatingstates including: a display-element-off operating state, in which thesecond operating mode is not activatable, a display-element-on operatingstate, in which the second operating mode is active, and an intermediatestate, in which the cruise controller is in an inactive state, but isactivatable.